Residents near a DuPont plant in West Virginia say that the company emitted a toxic chemical into their drinking, C-8 a checmical actually called Perfluorooctane sulfonic acid or perfluorooctane sulfonate (PFOS), making them sick, they say.

On Monday, DuPont will face the first trial involving Carla Marie Bartlett who says she developed kidney cancer from contaminated water. She is one of 3500 plaintiffs. Her case will be the first case to go to trial, in an early test of potential liability for the allegedly decades-long leak. A second trial will start Nov.

The lawsuits concern DuPont’s Washington Works plant in Parkersburg, West Virginia. There the company used C-8 as a processing aid to make products like Teflon non-stick cookware.

Plaintiffs say DuPont used C-8 at the plant since the 1950s and continued even after learning that it was potentially toxic and that it had been discovered in nearby drinking water supplies in Ohio and West Virginia.

In 2001, a class action was filed against DuPont over C-8 exposure. DuPont settled in 2004, agreeing to It also agreed to convene a panel of scientists to determine whether any diseases were linked to C-8. That very panel concluded there was a probable link between C-8 and six diseases: kidney and testicular cancer, ulcerative colitis, thyroid disease, pregnancy-induced hypertension and high cholesterol.

Class members with one of those diseases then individually sued DuPont. The company agreed not to challenge whether C-8 can cause those diseases, but plaintiffs still must prove it is to blame for their individual illnesses.